1. Field of the Invention
This invention relates to apparatus for making a fibrous web comprising a feeder for receiving a feed web, a plurality of serrated carding drums rotating in the same sense at a surface speed which permits the fibers on the drums to fly from the latter under centrifugal force, and an air-permeable collecting surface, which is continually moved and from which air is sucked, and wherein fibers of the preliminary web fly from the carding drums in respective partial streams, which impinge on the collecting surface at points spaced apart in the direction of travel of the collecting surface, the carding drums are arranged one behind the other in the direction of movement of the feed web and are closely spaced apart, and each carding drum which succeeds another in the direction of travel of the feed web constitutes a worker roller associated with the preceding carding drum.
2. Description of the Prior Art
Because in apparatus of the kind described the carding drums closely succeed each other, each succeeding carding drum can act like a worker roller to comb the fibrous material which is delivered by the preceding carding drum so that the combed-out fibers are thrown off onto the collecting surface immediately after they have been combed out. This will result in an adequate opening of the feed web and will permit a division of the feed web into a plurality of partial streams of fibers in a simple manner because each succeeding carding drum effects an additional combing operation, which provides fibrous material for at least one additional partial stream. The partial stream of fibers which fly from each carding drum may have a low fiber density even if the throughput rate of fibrous material through the apparatus is relatively high. A highly uniform web can be obtained owing to that low fiber density of the fibrous streams and to the fact that the fibers are deposited on the collecting surface in a plurality of layers. But in spite of the high throughput rate which is permissible, the opening capacity of the carding drums is restricted so that the speed of travel of the feed web cannot be increased as highly as may be desired.